Asphalts used in the construction of roads typically harden and become less flexible after the asphaltic paving mixture has been applied. Even though the typical paving mixture contains only a relatively small amount of asphalt, the remainder being comprised of inorganic aggregates and fillers, it is the asphalt that provides the resiliency and elasticity of the paving material necessary for proper performance. Thus the loss of flexibility causes road cracking and deterioration over a period of time. Softer grades of asphalt have been employed in an attempt to prevent cracking, but they reduce the compressive strength of the road and allow rutting to occur.
Much of the hardening comes about as a result of oxidative condensation of the asphalt. Chemical anti-oxidants have been proposed, but they are not completely satisfactory due to cost and processing requirements. It would be especially advantageous to have available an additive which not only would prevent oxidative condensation reactions from taking place, but would be inexpensive and readily available to the asphalt producer.